Economic values of ecosystems services

Sunday 7th August. We spend the day in Akkeshi Marine Station Field Science Center for Northern Biosphere of Hokkaido University. In the afternoon, we had an engaging presentation from Professor Nakaoka Masahiro.
One point especially draws my attention. He displays a diagram assessing the economic values per hectare per year of ecosystem services  (Costanza et al., 1997). He highlighted the fact that this kind of data had been largely criticized by academics as well as the stakeholders involved in ecosystem services who claim that their activity had been under-evaluated. Calculating the economic value of ecosystem services involves a great number of unknown or unquantifiable variables and it seems that there cannot be a common agreement on the output of the study. However, i would like to question the very reason that gives incentive to investigate the economic value of nature.
I assume that one main argument is that for some people, the only valuable perspective on an issue is the economic scope, and then assessing the economic value of ecosystem services may lead them to pay closer attention to ecosystem. Thus, this monetary quantification of Nature is a pragmactic mean to make financial-minded stakeholders, considering ecosystem as something that worth be defending. However, the weakness of this method is that ultimately, Nature is not and must not be an economic resource. As long as we quantify its economic value, market principles apply and ethics disappear. Hence, our relation to Nature is definitely moral and ethics. Nature provides us the mean for subsistence, we owe our life to it, we take refuge in it. Therefore, i am against any attempt to break down ecosystems to a mere system for us to provide services that can be valued by economic markets.